Apparatus controlling the brightness of lamps



May 26, 1970 Filed Oct. 23, 1967 A. 1.. ISAACS 3,514,670

APPARATUS CONTROLLING THE BRIGHTNESS OF LAMPS 2 Sheets-Sheet 1 15, 17 I4) MASTER c0125 00/25 050. DRIVERS STORE BUFFER -19 STORE 400 l I f I6 D/A RAISE/ cow. DIM UNIT x 43- ""44 0/! INPUT sew/v5? SCANNER 42 40 l IT; I 20 D/MMER CONTROL co/vmoL URN/5 ulwr u/v/r CHANNEL Q CONTROL 10- DIMMERS 55L UNIT I I A 13 9 T0 LAMPS 1.

ANTHONY LEONARD ISAACS INVENTOR BY 1g ATTORNEY y 1970 I A. L. lsAAcs 3,514,670

APPARATUS CONTROLLING THE BRIGHTNESS OF LAMPS Filed Oct. 23, 1967 2 Sheets-Sheet 2 PULSE g 29 SHAPER 4/ 22 DIM l I l l l 47 ANTHONY LEONARD ISAACS INVENTOR BY 3, r

A TORNEY United States Patent Olfice 3,514,670 Patented May 26, 1970 3,514,670 APPARATUS CONTROLLING THE BRIGHTNESS OF LAMPS Anthony Leonard Isaacs, London, England, asslgnor to Thorn Electronic Limited, London, England Filed Oct. 23, 1967, Ser. No. 677,275 Claims priority, application Great Britain, Oct. 21, 1966, 47,343/ 66 Int. Cl. H05b 37/02 US. Cl. 315-492 7 Claims ABSTRACT OF THE DISCLOSURE Apparatus for changing lamp brightness, in which a contact has voltage applied to it intermittently by a rotating member, and electronic apparatus, in a circuit including the contact and the lamp, responsive to the ire quency with which voltage is applied to the contact so that it changes the brightness of the lamp at a rate dependent on said frequency. The rotating member contains magnets which actuate contacts in reed switches. The circuitry is arranged so that it will either dim or raise the brightness, depending on which of two reed switches is closed first.

The present invention relates to apparatus for controlling the brightness of lamps, particularly but not exclusively lamps used in stage and studio lighting.

According to the present invention there is provided apparatus for changing lamp brightness comprising a contact, control means for intermittently applying a voltage to the contact including a member mounted for manual rotation about a shaft to pass adjacent to the contact and apply a signal thereto, the apparatus also comprising brightness-setting means, electrically coupled to the contact for changing the brightness of a lamp at a rate dependent on the frequency with which the signal is applied to the contact.

A pair of contacts may be provided, one contact being that mentioned in the preceding paragraph, and the other being for connection to a voltage source. The contacts may then be opened or closed as the member passes adjacent during rotation. For example, the member could be a cam closing the pair of contacts during rotation, or, if the contacts are those of a reed switch, the member could be a wheel with one or more magnets mounted in its periphery.

A thumb-wheel, hand-wheel or lever may be fixed to the shaft and used to rotate the member.

In stage lighting system, for example, it is advantageous to rotate a thumb wheel in one direction to increase, that is raise, brightness and in the other direction to decrease, that is dim, brightness. Thus it is useful if raise and dim outputs are wire encoded, and appear on one of two wires depending on which way the thumb wheel is rotated.

According to another aspect of the invention therefore there is provided apparatus for sensing the direction of rotation of a member, comprising a member mounted for rotation about a shaft to pass adjacent to first and second contacts and apply a voltage thereto, first direction-indicating means for providing an output signal if a voltage is applied to the first contact before the second, and second direction-indicating means for providing an output signal if a voltage is applied to the second contact before the first.

Preferably two reed switches adjacent to one another are provided, these switches being actuated one after the other as the wheel carrying the magnets is rotated. In this way two related trains of pulses appear, the phase of one being retarded in relation to the other and hence indicating the direction of rotation of the wheel, that is whether the lamp is to be made more or less bright. The leading. edges of one pulse train, or short pulses derived therefrom may be passed to two AND gates, one having another input from the other pulse train, and the other AND gate having another input which is the complement of the other pulse train. One of the AND gates will then be opened when the lamp brightness is to be increased, and the other AND gate will be opened when the lamp is to be dimmed. If the AND gate outputs are connected to raise and dim wires pulses from these gates will be wire encoded.

Where the control means are rotated by a lever, outputs on raise and dim wires may be provided by means responsive to lever position, for example changeover switches or reed switches. Then moving the lever in one direction in a raise sector of movement increases brightness and in the other direction in a dim sector of movement decreases brightness.

Several lamps or groups of lamps may be selectively controlled by apparatus according to the invention. For example each group of lamps may be allocated a channel in a time-divided system and several sets of apparatus according to the invention may be selectively allocated to each channel. Pulses representative of the speed of opening of a number of pairs of contacts, for example the short pulses which pass through the above mentioned AND gates, are made long enough to last for one complete cycle of channels and are passed to a matrix of AND gates, one gate for each set of apparatus. The matrixed AND gates are connected to a scanning pulse source by way of a selector which is set so that selected gates,

corresponding to the selected channels receive enabling input. Thus pulses derived from the short pulses appear in the selected channels only. Over a number of cycles of channels, pulses will appear on raise or dim wires from the matrix in the selected channels every cycle or less depending on the speed of rotation of the said member. The raise and dim wires are connected to means for changing the brightness of the groups of lamps which are scanned in accordance with the time-divided channels.

In order to ensure one-for one correspondence between the short pulses and the pulses in the selected channels, a two-state register is provided for each set of apparatus which is triggered into a first state by the leading edge of each first short pulse, and triggered into its second state at the end of the period of the channel selected for that set of apparatus. When in its first state the two-state register is applied as an enabling signal to the matrixed AND gates.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a block diagram of a stage lighting system,

FIG. 2 is a schematic diagram of apparatus according to the invention, used in the system of FIG. 1 as a control unit, and

FIG. 3 shows pulse waveforms useful in explaining the invention.

In the stage lighting system of FIG. 1 a bank 10 of dimmers controls groups of lamps (not shown). The intensity of light from any group can be changed by rotating a thumb-wheel control of any of ten control units, three of which 7, 8 and 9 are shown. It a thumb wheel is rotated in one direction the brightness of a group of lamps selected by a channel selector 13 is continuously increased, at a rate depending on the speed of rotation of the thumb wheel. Rotation in the other direction decreases the brightness of the lamps in the group.

'Each group of lamps is allocated a channel and eight cores in a core store 14. One of the cores registers a onebit On Off signal, and the other seven register a seven bit brightness count giwing the required brightness for the group of lamps. The channels are time divided and for this purpose a 40 kc./s. master oscillator supplies pulses to a divider circuit 16, having two cascaded divide-by-ten stages and two cascaded divide-by-two stages. The first divide-by-ten stage gives a units output, the second divideby-ten stage gives a tens output, and the two divide-bytwo stages gives a four state hundreds output. The channels are numbered from one to four hundred and have a duration of twenty-five microseconds. The outputs from the divider circuit are passed to core drivers 17, which at the beginning of each twenty-five micro-second channel period, using the conventional half current pulses applied to X and Y axis wires of the matrix of the store 14, select the eight cores allocated to one of the channels and transfer their contents to a butter store 18. The contents of the buffer store is then converted to an analogue voltage by a digital to analogue converter 19. The resultant voltage is passed to a selected dimmer drive unit 20, by an output scanner 21 comprising a sampling matrix of AND gates controlled by the outputs of the divider circuit 16 feeding four hundred reservoir capacitors. The sampling matrix, timed from the main divider waveforms, decommutates the 400-channel time sequential signal from the digitalto analogue convertor 19 into four hundred parallel signals on the four hundred reservoir capacitors. These signals, one per lighting channel, are shaped in the dimmer drive units 20 into signals controlling the four hundred dimmers, one per lighting channel.

At the end of each twenty-five micro-second period the contents of the buffer store are read back into the core store, and the contents of the next eight cores corresponding to the next channel are read into the buffer store.

The ten control units are used to enter the desired brightness counts into the store 14 and to change them as necessary. One of these control units will now be described with reference to FIG. 2. A wheel 22 and a shaft 23 are rotated by means of a thumb wheel, hand wheel or lever attached to the shaft. As the wheel rotates magnets 24, 25, 26 and 27 set in its periphery pass adjacent to two reed switches 28 and 29, closing the switches intermittently. In practice magnets would be evenly distributed throughout the whole periphery of the wheel 22. One contact of each reed switch is connected to a voltage source V, and the other contacts of the switches are connected through resistors 30 and 31 respectively to earth. Thus, if the wheel 22 is rotated clockwise, pulses 32 (see FIG. 3(a)) appear at the input to a pulse-shaper circuit 33 and pulses 34 appear the input to a complement-forming circuit 35. The pulse-shaper circuit 33 provides short pulses 36, coincident with the leading edges of the pulses 32, and the complement-forming circuit provides the pulses 37 which are complementary to the pulses 34. The pulses 34 and 36 are passed to an AND gate 38, and the pulses 36 and 37 are passed to an AND gate 39. Hence for clockwise rotation of the wheel 22 the AND gate 39 opens and passes the pulses 36 to a Raise output wire 40. If the wheel 22 is rotated in a counter clockwise direction the leading edge of the pulses 34 appear before the pulses 32, the pulses 36 and 34 are coincident and the AND gate 38 allows the pulses 36 to reach a Dim output wire 41.

The wires 40 and 41 are connected to an input scanner 42 which is used to time the pulses 36 so that pulses derived therefrom appear only in channels selected using the channel selector 13. The channel selector panel has ten lOs buttons marked 0, 10, 20 80 and 90* and four 100s buttons marked 0, 100, 200 and 300 respectively. There are two registers or stores in the channel selector 13, a ten-state 10s register (states 0, 10, 20, 80 and 90) and a four-state 100s register (states 0, 100, 200 and 300). If the 200 button is depressed and released the 100s register is set to its 200 state, lightning a signal lamp within or near the 200 button and extinguishing all other 100s" signal lamps.

This condition is sustained until another l00s button is operated. If now the 70 button is depressed and released the l0s register is set to its 70 state, lighting a signal lamp within or near the 70 button and extinguishing all other lOs signal lamps. The control units 0 to 9 now operate on channels 270 to 279 respectively of the 400 channels available, controlling the lamps in lighting channels 270 to 279. If the 10s button 0 is now depressed the 10s register is set to its state 0, 10s button 0 is illuminated instead of button 70 and the control units 0 to 9 operate on channels 200 to 209 respectively. If s button 0 is next depressed the 100s register is set to 0, l00s button 0 is illuminated instead of the 200 button and the control units 0 to 9 operate on channels 0 to 9 respectively.

With the channel selector set to 270, the l00s and 10s registers in the channel selector are compared in an AND gate matrix with the corresponding counters of the divider circuit 16 to produce an output pulse when the divider circuit is in states 270 to 279.

Each output wire of the control units is connected to an AND-gate matrix together with the units output of the main divider and the output of the channel selector. The pulses 36 are made longer than one cycle of channels so that with the 200 and 70 buttons illuminated pulses appear in a raise output wire 43 or a dim output wire 44 of the input scanner 42 from the control unit 0 when the divider is in the state 270 from the control unit 1 when the divider is in the state 271 etc., and from the control unit 9 when the divider is in the state 279.

Each control unit also has an associated two state register (not shown) to ensure one to one correspondence between pulses in the channels and pulses from the control units. FIG. 3(d) shows one of the pulses 36 to an enlarged time scale, and shows this pulse spanning a number of complete cycles 45 of channels. The two state register is triggered into one state 46 at the beginning of each pulse 36 (FIG. 3(e)) and triggered into its other state 47 at the end of the period of the channel selected for the associated control unit. The two-state register is connected to provide an enabling pulse to that AND gate in the input scanner connected to the associated control unit. Pulses 36 do not therefore appear on wires 43 or 44 during the last three cycles 45 spanned by the illustrated pulse 36 FIG. 3(d).

The pulses 36 may be made 12.5 ms. in duration, for example, to ensure spanning one cycle of channels. With this pulse width the wire encoding system can operate at reed-switch pulse rates up to 20 pulses per second when the 12.5 ms. pulse occupies one quarter cycle of the reedswitch output waveform.

When the brightness count of a group of lamps, represented by the states of the eight cores allocated to that group has been read into the buffer store 18, a raise/dim unit 48 raises or lowers the count at one unit per pulse received along the Wires 43 or 44. Thus for example if the thumb wheel of the control unit 7 were rotated in a clockwise direction and if the control unit 7 were coupled to channel 277, the count stored by the cores allocated to that channel would be raised.

The brightness count for any selected channel may thus be wound up and down by the thumb-wheel, or hand-wheel, or raised and lowered by ratchet and pawl action of the lever in the appropriate sector of its travel. There is no one-to-one relationship between control shaft position and lamp brightness because the shaft may be disengaged from a given control channel and re-engaged in a different relative attitude.

Many other embodiments of the invention will be apparent. For example the rotating member could be a wiper connected to a voltage source, and making contact with one of two separately connected contacts, before the other in one direction of rotation, and vice-versa in the other direction. As has been mentioned the rotating member may be a cam, or toothed wheel which comes into contact with a moving contact of a pair of contacts pushing the moving contact against a stationary contact.

I claim:

1. Apparatus for changing lamp brightness comprising a contact,

control means for intermittently applying a voltage to the contact,

said control means comprising a control member for co-operation with the contact and a shaft mounting said control member for manual rotation and brightness-setting means electrically coupled between the contact and the lamp to change the brightness of the lamp at a rate dependent on the frequency with which the voltage is applied to the contact.

2. Apparatus as claimed in claim 1 including a further contact connected to a voltage source, said control member comprising means to engage and disengage said further contact with said first contact.

3. Apparatus as claimed in claim 2 wherein said first contact and said further contact form the contacts of a magnetically-operable reed switch, and said control member is a wheel having magnets mounted around its periphery.

4. Apparatus for changing lamp brightness as claimed in claim 1 having a second contact to which a voltage is intermittently applied by the rotation of the control member, the second contact being spaced from the first contact around the shaft, a first direction-indicating means coupled between the first and second contacts on the one hand and the brightness-setting means on the other hand to change the brightness in one sense if a voltage is applied to the first contact before the second, and a second direction-indicating means coupled between the first and second contacts on the one hand and the brightness-setting means on the other hand to change the brightness in the ,opposite sense if a voltage is applied to the second contact before the first.

5. Apparatus as claimed in claim 4 in which the first and second contacts are each one of a pair of contacts of a separate reed switch and the member is a wheel carrying magnets around its periphery which actuate the switches one after the other as the wheel rotates, thereby generating two trains of pulses one of which is displaced in phase relative to the other in a direction determined by the sense of rotation, and in which the first directionindicating means is an AND gate receiving one pulse train and the leading edges of the other pulse train and the second direction-indicating means comprises a second AND gate and means for generating the complement of the said one pulse train, said complement being applied to the second AND gate together with the leading edges of the other pulse train.

6. A system for controlling the brightness of several groups of lamps comprising a number of sets of apparatus as claimed in claim 5 with their first direction indicating means each connected to a different one of a first matrix of AND gates and their second directionindicatin-g means each connected to a different one of a second matrix of AND gates, the two matrices being connected to a scanning pulse source by way of a selector which is set so that only selected gates, corresponding to selected ones of a plurality of time-divided channels for individual control of the several groups of lamps, receive enabling inputs, the outputs of the direction-indicating means being shaped to give pulses of a length covering one complete cycle of channels so that a pulse is passed to a brightness-setting means associated with a group of lamps when an enabling input is received by a selected gate, the brightness-setting means being scanned by the scanning pulse source.

7. A system as claimed in claim 6 including a two-state register for each set of apparatus, the register being triggered into a first state by the leading edge of each first output pulse from the direction indicating means and triggered into its second state at the end of the period of the channel selected for that set of apparatus, the output of the register in its first state being applied as an enabling signal to the matrices of AND gates.

References Cited UNITED STATES PATENTS 2,994,804- 8/1961 Skirpan 315297 X 3,004,193 10/1961 Bentham et al. 315-316 X 3,221,214 11/1965 Wolff et a1. 315292 3,358,237 12/1967 Houle 307218 X JOHN W. HU'CKERT, Primary Examiner R. F. POLISSACK, Assistant Examiner US. Cl. X.R. 

